1. Field of the Invention
The present invention relates to a method of making light-trapping members having inclined piles and more particularly to a method of making light-trapping members to be attached to a film passage mouth of a photographic film cassette in which a film leader is advanced out of the photographic film cassette through the film passage mouth.
2. Description of the Related Art
Recently, photographic film cassettes, in which an entire photographic film is wound on a spool and contained in a cassette shell in order to facilitate the loading of the photographic film cassette into a camera, have been utilized. The maximum diameter of the roll of photographic film is approximately equal to or smaller than the inside diameter of the cassette shell to prevent loosening of the roll of photographic film. In such a photographic film cassette, the leading end of the photographic film is advanced out of the cassette shell, through a film passage mouth, by rotating the spool in a film advancing direction.
In order to prevent external light from entering into the cassette shell through the film passage mouth, light-trapping members are attached to the upper and lower inside surfaces of the film passage mouth. When the leading end is advanced out of the cassette shell by rotation of the spool, a large advancing torque is required so as to prevent the leading end from being caught by the light-trapping members. Therefore, if conventional light-trapping members, such as plushes, are attached to the film passage mouth of the cassette shell, the leading end needs to pass through the film passage mouth while disentangling any entangled piles of the plushes, which causes the leading end to encounter a very large resistance due to interaction with the plushes.
Therefore, it is necessary to use light-trapping members having inclined piles in order to reduce the advancing torque. The piles need to be inclined from the roots thereof at a constant angle with respect to a base fabric of the light-trapping members. The piles in each row overlie the piles in an adjacent row. The light-trapping members are attached to the film passage mouth such that the inclination of the piles is directed toward the film advancing direction. As disclosed in Japanese Patent Laid-Open Publication No. 4-22944, piles can be raised by a brushing roller.
If a web is brushed to incline its piles and is slit thinly to obtain ribbons having the same width as the light-trapping members, tips of inclined piles are cut and a large amount of dust is thus generated. Accordingly, it is preferable to weave a ribbon having the same width as the light-trapping members or to slit a web into a number of ribbons prior to imparting inclination to their piles. The ribbons is cut by a length equal to the width of the film passage mouth. However, when inclining the piles of a thin ribbon with the brushing roller, the ribbon tends to be twisted due to its thinness, resulting in irregular inclinations of the piles.